The construction of an intake air heating device of the prior art has been such that the device includes a flame baffle cylinder, a combustion chamber and a fuel injection nozzle, and the flame baffle cylinder is located within an intake pipe, so as to introduce combustion gases from the outer periphery of the flame baffle cylinder into the intake pipe. Such an intake air heating device has been widely known, for example, as a combustion type, intake air heating device.
The intake air heating device of the prior art, however, must be secured to the linear portion of an intake pipe, because of its construction failing to accommodate itself to the bent elbow portion. Should the intake air heating device of the type be secured to the elbow portion, there would arise a difference in the velosity of streams of intake air flowing through the transverse cross sectional area of the elbow portion of the pipe, leading to the failure to provide satisfactory combustion as well as the failure to maintain the well balanced temperature for intake air, and thus the intake air heating device could not fulfil its inherent function.
In the meantime, an intake pipe leading to a Diesel engine, in most cases, has an elbow portion because of the construction of the engine itself, and there occasionally arises the need to secure the intake air heating device to the elbow portion of the intake pipe from the viewpoint of space, etc. In such a case, the type of an engine to which the intake air heating device can be secured has to be limited, because of the construction of the device itself.